1. Field of the Invention
Molecules, including proteins, may be engineered through modification of the structural, catalytic and/or binding properties, as well as for the de novo design of artificial molecules. Molecular or protein engineering relies on an efficient recognition mechanism for incorporating desired amino acid residues in specifically chosen locations of the protein sequence or structural region. This process has been very useful for designing new macromolecules with precise control of composition and architecture; however, a major limitation exists when the mutagenesis is restricted to the 20 naturally occurring amino acids. For this reason, it is becoming increasingly clear that incorporation of non-natural amino acids can extend the scope and impact of molecular and protein engineering methods. Thus, for many applications of designed macromolecules, it would be desirable to develop methods for incorporating amino acids that have novel chemical functionality not possessed by the 20 amino acids commonly found in naturally occuring proteins, or to utilize a non-natural amino acid residue for an anchoring position for further chemical or biological modification.
For example, if certain changes in a protein or other molecule are desired (such as the size, acidity, nucleophilicity, hydrogen-bonding or hydrophobic properties, or other properties of amino acids) to fulfill a specific structural or functional property of interest, it would be advantageous to incorporate non-natural amino acid residues into the molecule. Such an advantage would greatly expand the ability to rationally and systematically manipulate the structures of proteins, in order to probe protein function, modify existing proteins, and create artificial proteins with new properties.
2. Description of the Related Art
Proteins are synthesized through a process beginning with RNA transcription from DNA, followed by protein translation in the cell. In order for translation to occur, a ribosome binds to a messenger RNA (mRNA) that has been transcribed from DNA. During translation, each transfer RNA (tRNA) is matched with its cognate amino acid by a collection of enzymes called aminoacyl-tRNA synthetases (AARS). The AARS charge each tRNA with the appropriate amino acid, thereby facilitating translation of the mRNA. As the process continues, the protein is elongated by the addition of the amino acids by the AARS.
Most cells make twenty different AARS, each corresponding to one of the twenty naturally occurring amino acids. The AARS enzymes function optimally with its own cognate amino acid and set of tRNA molecules appropriate to that amino acid.
Proteins may be modified or synthesized de novo through protein engineering techniques. In particular, proteins may be altered or modified to delete, substitute or add amino acids or modify existing amino acids. For example, it may be desirable to change at least one particular characteristic of a protein in order to develop a novel chemical functionality. Such characteristics may include the size, acidity, nucleophilicity, hydrogen-bonding or hydrophilic properties of certain amino acids in a protein.
Modifying molecules, including proteins, is presently largely inefficient and ineffective, with large batch-to-batch variations in quality and quantity produced. In this regard, it would be beneficial to develop an efficient method for designing molecules, including proteins, with improved properties and attached chemical moieties. The present invention provides such an advantage, as well as many others that are expressed or implied in the present disclosure.